I'd like to create a new subsection command with the same calling structure like the original one, but I have no idea on how to handle the case when the optional argument is omitted. Basically I want to have newsubsection[Short Title]{Long Title} to call subsection[#1]{#2} and newsubsection{Title} to call subsection{#1}.

I've read the thread about a similar problem posted here around two years ago, but it seems to have been much more complicated (more than one opt-argument) and I'm too much of a TeX-newbie to transfer the solutions to my problem.

Also, I already tried lots of weird combinations like \newcommand{\subsect}[2][#1]{\par\nolinenumbers\subsection[#1]{#2}\linenumbers} (failed attempt to use the syntax from the \wbalTwo-example here), but none of them were resulting in anything remotely working.

How would you trigger something after\@newsubsection using \@dblarg using your setup? That seems to be what the OP is after.
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WernerJan 20 '13 at 19:54

@Werner Not sure what you mean \@newsubsection could have more than two arguments if you need to pick up more. Or of course it can end with a macro that takes arguments? But the example given in the question doesn't seem to need that?
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David CarlisleJan 20 '13 at 19:59

@David Carlisle Thanks for providing an alternate method. Unfortunately I am not able to transfer your code to my problem, here is what I've tried. Any further advice is appreciated.
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Big-BlueJan 21 '13 at 13:00